Method for producing a cementitious building panel with tapered edges transverse to the direction of a production line in a continuous production process

Abstract

A method for producing a cementitious building panel (1) with tapered edges transverse to the direction of a production line in a continuous production process, comprising the steps of: - transporting a cementitious building panel (1) on a first conveyor belt (21) and - embossing the cementitious building panel (1) with a rotating roller (3) by vertically moving the rotating roller (3) so as to provide a cementitious building panel (1) with tapered edges transverse to the direction of a production line.

Description

[0001] Method for producing a cementitious building panel with tapered edges transverse to the direction of a production line in a continuous production process

[0002] The invention relates to a method for producing a building panel, especially a cementitious building panel, with tapered edges transverse to the direction of a production line in a continuous production process and an apparatus according to the respective independent claim.

[0003] The technical field relates to the production of building panels, e. g. the production of gypsum building panels.

[0004] Cementitious building panels, like gypsum plasterboards and gypsum fiberboards, are widely used in drywall construction, for example, in the cladding of walls or ceilings. Thereby, several building panels are fixed to a grid resulting in the abutting of panel edges. To obtain a cohesive surface which is closed over the entire surface area, the individual panels are grouted with joint tape and filler. Doing so with even faced panels results in unevenness in the surface along the edges of the panels. Thus, it is common to produce cementitious building panels with tapered edges to place the tapes onto so they do not protrude the even surface.

[0005] Cementitious building panels are shaped from a cementitious material. Within the scope of this document, the term “cementitious material” is used for such materials that are based on settable pasty compositions, especially slurries of a binder material - generally in presence of further co-components - in water. In general, the setting process is a chemical reaction, especially a chemical reaction involving water. The term “cementitious material” is used for the settable composition itself, for the already set product as well as for the intermediate states during setting. Especially, cementitious materials comprise compositions wherein the binder is cement and / or a cement modification and / or gypsum (calcium sulfate dihydrate) and / or a calcium-sulfate modification (like further hydration levels of calcium sulfate like anhydrite, a- hemihydrate, p-hemihydrate, bassanite, selenite). The production of cementitious building panels with or without tapered edges comprises several steps: A slurry is formed by a binder, water and additives and then inserted between two layers of paper. In a continuous production process the wet cementitious building panel is then transported via conveyor belts and undergoes several processing steps such as pressing into form, drying and cutting.

[0006] Shaping the tapered edges of the cementitious building panel is also part of these steps. While it is easy to shape the long side edge with elevations at the edges of the conveyor belt, it is technically a lot more complex to integrate the shaping of the tapered edges that are transverse to the direction of the production line into a continuous production process.

[0007] One exemplary production method is to position a roller with at least one elevation beneath the conveyor belt whereby the elevation presses into the cementitious building panel as it is transported by the conveyor belt. However, the elevations wear off over time and do not allow a variation of the tapering in depth or form without switching the roller.

[0008] Another way is to press a stamp into the cementitious building panel whereby the stamp travels at the same speed as the panel while being pressed up. This means that the stamp must be movable in at least two directions requiring a complex control system and additional engines for horizontal movement.

[0009] To overcome the problems known in the prior art, the invention provides a method for producing a building panel, especially a cementitious building panel, with tapered edges transverse to the direction of a production line in a continuous production process and an apparatus according to the respective independent claim. Advantageous aspects are the subject matter of the dependent claims.

[0010] The invention comprises a method for producing a building panel, with tapered edges transverse to the direction of a production line in a continuous production process, comprising the steps of:

[0011] - transporting a building panel on a first conveyor belt and

[0012] - embossing the building panel with a rotating roller by vertically moving the rotating roller so as to provide a building panel with tapered edges transverse to the direction of a production line. In particular, the building panel is a building panel based on a settable material, most particular it is a cementitious building panel. Accordingly, hereinafter, it is designated as a cementitious building panel. However, the descriptions and specifications for the method according to the invention are meant to be likewise applicable for producing non-cementitious building panels. As a roller that is vertically movable is used elevations on the roller are not required. This way a component that wears out quickly is eliminated. Additionally, the roller does not have to be moved horizontally with the cementitious building panel in order to avoid shear forces as it is rotating.

[0013] According to one advantageous aspect the method further comprises transporting the cementitious building panel with constant speed into direction A and embossing at a time when the cementitious building panel has just hardened to such a degree that no reshaping of the cementitious building panel occurs afterwards. The right adjustment of the time of embossing the cementitious building panel is crucial. This is due to the fact that cementitious building panels are produced faced-down. Thus, embossing too soon will mean that the slurry is still too wet and the embossment will get out of shape. However, embossing too late will require too much force and thus weaken the bonding between the slurry and the paper which may have unwanted blistering as consequence. For example, the embossing may take place at 10 to 25 seconds after the slurry exits the mixer in standard gypsum plasterboard production lines.

[0014] Preferably, the rotation of the rotating roller is actively driven. As the roller is moved upwards it lifts the conveyor belt from the rollers that drive the conveyor belt forward. Thus, the rotating roller carries the conveyor belt.

[0015] Furthermore, the rotating roller presses the first conveyor belt against the cementitious building panel during the vertical movement. Thereby, the cementitious building panel is being embossed. As the vertical movement of the rotating roller can be varied, so can the dimension of the embossment.

[0016] Advantageously, a second conveyor belt positioned opposite of the first conveyor belt in such a way that the cementitious building panel is transported between the first and the second conveyor belt. The second conveyor belt moves with the same speed as the first belt does. According to a preferred aspect, the first and second conveyor belts are simultaneously in contact with the cementitious building panel during production. The position of the belt can be adjusted to the thickness of the cementitious building panel. As the conveyor belts are moving with the same speed no shear forces occur due to the contact of both conveyor belts to the cementitious building panel.

[0017] Furthermore, the method comprises pressing the cementitious building panel against a first belt supporting plate positioned opposite of the rotating roller in sliding contact behind the second conveyor belt upon embossing. The first belt supporting plate supports the stability of the second conveyor belt. This way the back of the cementitious building panel is not deformed when the face is being embossed by the rotating roller.

[0018] Preferably, the method further comprises extruding the cementitious building panel between the first and a second belt supporting plate wherein the second belt supporting plate is positioned in sliding contact behind the first conveyor belt. Therein, the first and the second belt supporting plates are angled to each other. The angle between the belt supporting belt may amount to 0.1 ° to 0.5 °.

[0019] According to another advantageous aspect the first and the second belt supporting plate extrude the cementitious building panel with a tolerance of 0.1 mm to 0.5 mm in thickness. This way, unevenness exceeding the tolerance in the face and back of the cementitious building panel are be smoothed out.

[0020] Additionally, the intensity of the embossment in the cementitious building panel is varied by the deflection of the rotating roller’s vertical movement from 10 % to 80 % of the thickness of the cementitious building panel. Both the depth and the width of the of the embossment can be adjusted. The absolute depth may amount to 0.2 mm to 10 mm depending on the thickness of the cementitious building panel and the joint tape that is expected to be in use.

[0021] Another aspect of the invention relates to an apparatus for producing a building panel, especially a gypsum plasterboard or a gypsum fiberboard, with tapered edges transverse to the direction of the production line in a continuous production process comprising:

[0022] - a first conveyor belt for transporting a cementitious building panel and

[0023] - a rotating roller actively rotatable and vertically movable to emboss the building panel as to provide a building panel with tapered edges transverse to the direction of a production line. The apparatus can be freely integrated into the production line independent from how many steps may occur before or after the apparatus. Thus, it is possible to position the apparatus according to the required condition of the slurry throughout the production line.

[0024] Furthermore the apparatus comprises

[0025] - a second conveyor belt, wherein the cementitious building panel is transported between the first and the second conveyor belt,

[0026] - a first belt supporting plate, wherein the building panel is pressed against upon being embossed and

[0027] - a second belt supporting plate, wherein the first belt supporting plate and the second belt supporting plate are angled and positioned in such a way so that they act as an extruder.

[0028] The belt supporting plates may be stone plates, yet can also be made of other materials.

[0029] As already mentioned, the building panel particularly is a building panel based on a settable material, most particular it is a cementitious building panel. Again, hereinafter, it is designated as a cementitious building panel, but the descriptions and specifications for the apparatus according to the invention are meant to be likewise applicable for the production of non- cementitious building panels.

[0030] Advantageously, the rotating roller is shaped convex along its length. This is to equalize the deflection of the roller upon pressing against the cementitious building panel and additionally prevents too much pressure on a possible long side tapered edge strip.

[0031] According to an exemplary embodiment of the invention, the rotating roller and the first belt supporting plate are positioned beneath the first conveyor belt and the second belt supporting plate above the second conveyor belt, respectively. Placing the rotating roller beneath the first conveyor belt makes it possible to have one continuous conveyor belt throughout the apparatus. This reduces stress and the risk of deformation due to a transition from one belt to another. The belt supporting plates are not in direct contact with the cementitious building panel to avoid shear forces that may damage the bonding between slurry and paper.

[0032] Preferably, the second belt supporting plate and the first conveyor belt are mounted on a frame, wherein the frame is vertically movable. The movement of the frame as of the rotating roller may be driven by electro cylinders or servo motors. In the following drawings, the invention is illustrated in context of exemplary embodiments, in which

[0033] Fig. 1 shows a schematic illustration of the apparatus with the second conveyor belt in an upper position with the system not in use;

[0034] Fig. 2 shows a schematic illustration of the apparatus during the first step of the method, transporting the cementitious building panel;

[0035] Fig. 3 shows a schematic illustration of the apparatus during the second step of the method, embossing the cementitious building panel; and

[0036] Fig. 4 shows a schematic illustration of the apparatus during the third step of the method, extruding the cementitious building panel.

[0037] Especially, the cementitious building panel of the embodiments shown in Fig. 1 to Fig. 4 is a gypsum building panel, for example a gypsum plasterboard or a gypsum fiberboard.

[0038] Fig. 1 shows a schematic illustration of an exemplary embodiment of the apparatus 10 with the first conveyor belt 21 and the rotating roller 3 as it is not in use. The cementitious building panel 1 is transported by the first conveyor belt 21. The first conveyor belt 21 may have continuous elevations on both its edges for shaping the long side tapered edges of the cementitious building panel 1 .

[0039] The second conveyor belt 22 and the first belt supporting plate 41 are placed above the first conveyor belt 21 and the cementitious building panel 1 on a frame 6 in a raised position in a distance of 200 to 250 mm to the first conveyor belt 21 . Beneath the first conveyor belt 21 the second belt supporting plate 42 is positioned in sliding contact to the first conveyor belt 21 as the first belt supporting plate 41 is in contact to the second conveyor belt. With the apparatus not in use the rotating roller 3 is in a lower position.

[0040] The rotating roller 3 is convex shaped along its long side. For example, the diameter at its edges and the middle may amount to 70 mm - 76 mmm - 70 mm. The convexity of the rotating roller 3 is preferable as to equalize the deflecting of the rotating roller 3 under pressure and a possible slack of the cementitious building panel 1 as the slurry is not perfectly hardened at the time right after embossing. Additionally, the pressure at the elevated edges on the long side of the first conveyor belt 21 is reduced.

[0041] The frame 6 is vertically movable. In this embodiment, the movement is driven by electric cylinders but it is also conceivable to use e. g. servo motors. The frame 6 will be lowered to a position in distance of 1 to 2 mm in order to use the apparatus 10.

[0042] The apparatus 10 in use is shown in Fig. 2. This illustration shows the first step of the method. The frame 6 with the second conveyor belt 22 and the first belt supporting plate 41 is in its lower position. In this position, the cementitious building panel 1 is transported by the first conveyor belt 21 with constant speed A through the apparatus 10. At this point, a certain amount of time has passed after the mixer so that the slurry of the cementitious building panel 1 has hardened to such a degree that no reshaping occurs after the cementitious building panel 1 is embossed.

[0043] In this step, the rotating roller 3 is in its lower position. However, its rotation is already actively driven in this position and it may already touch the first conveyor belt 21 but not elevate it. The length of the rotating roller 3 extends beyond the width of the first conveyor belt 21 and it is suspended on both of its sides.

[0044] As the frame 6 is in its lower position, the cementitious building panel 1 is transported between the first and the second conveyor belt 21 , 22. Thereby, the both conveyor belts 21 , 22 are moving at the same speed. This way no shear forces occur that may damage the cementitious building panel, especially the bonding between paper and slurry. Thereby, the first and second conveyor belts 21 ,22 are simultaneously in contact with the cementitious building panel 1 during production. This is given for cementitious building panels 1 of various thicknesses as the position of the frame 6 can be adjusted.

[0045] The second step of the method is shown in Fig. 3. The rotating roller 3 presses the first conveyor belt 21 against the cementitious building panel 1 and lifts it during the vertical movement from the rollers that otherwise carry the first conveyor belt 21. For moving the rotating roller 3 upwards or downwards electric cylinders are used in this embodiment. Thereby, the cementitious building panel 1 is pressed upon embossing against the first belt supporting plate 41 positioned opposite of the rotating roller 3 in sliding contact behind the second conveyor belt 22. The first belt supporting plate 41 is necessary as the second conveyor belt 22 would yield under the pressure of the cementitious building panel 1 . As the first conveyor belt 21 is pressed against cementitious building panel 1 , the slurry is embossed. The force of the rotating roller 3 is chosen as to deal no damage to the cementitious building panel 1 upon embossing. Too high force may cause blistering of the paper. The intensity of the embossment in the cementitious building panel is varied by the deflection of the vertical movement of the rotating roller 3 from 10 % to 80 % of the thickness of the cementitious building panel 1 .

[0046] Fig. 4 illustrates the apparatus 10 during the third step of the method. The rotating roller 3 no longer presses the first conveyor belt 21 against the cementitious building panel 1 and is now in a lower position. As shown, the embossment remains in the face of cementitious building panel 1 and is transported further to a second belt supporting plate 42 that is positioned in sliding contact behind the first conveyor belt 21. As the first belt supporting plate 41 extends to this point and the first and the second belt supporting plates 41 , 42 are angled to each other, the cementitious building panel 1 is extruded between them. The angle between the first and the second belt supporting plate amounts to 0.6 ° in this exemplary embodiment. The process of extruding ensures that the cementitious building panel 1 possesses the desired thickness with a tolerance of 0.1 mm to 0.5 mm in thickness. This also may reduce unevenness of the cementitious building panel 1 .

Claims

Claims1. A method for producing a building panel (1 ) with tapered edges transverse to the direction of a production line in a continuous production process, comprising the steps of:- transporting a building panel (1 ) on a first conveyor belt (21 ) and- embossing the building panel (1 ) with a rotating roller (3) by vertically moving the rotating roller (3) so as to provide a building panel (1 ) with tapered edges transverse to the direction of a production line.

2. The method according to claim 1 , further comprising transporting the building panel (1 ) with constant speed into direction A and embossing at a time when the building panel (1 ) has just hardened to such a degree that no reshaping of the building panel (1 ) occurs afterwards.

3. The method according to one of the preceding claims, wherein the rotation of the rotating roller (3) is actively driven.

4. The method according to one of the preceding claims, wherein the rotating roller (3) presses the first conveyor belt (21 ) against the building panel (1 ) during the vertical movement.

5. The method according to one of the preceding claims, wherein a second conveyor belt (22) positioned opposite of the first conveyor belt (21 ) in such a way that the building panel (1 ) is transported between the first and the second conveyor belt (21 , 22), especially wherein the first and second conveyor belts (21 , 22) are simultaneously in contact with the building panel (1 ) during production.

6. The method according to one of the preceding claims also comprising pressing the building panel (1 ) against a first belt supporting plate (41 ) positioned opposite of the rotating roller (3) in sliding contact behind the second conveyor belt (22) upon embossing.

7. The method according to one of the preceding claims further comprising extruding the building panel (1 ) between the first and a second belt supporting plate (41 , 42) wherein the second belt supporting plate (42) is positioned in sliding contact behind the first conveyor belt (21 ) and wherein the first and the second belt supporting plates (41 , 42) are angled to each other.

8. The method according to one of the preceding claims, wherein the first and the second belt supporting plate (41 , 42) extrude the building panel (1 ) with a tolerance of 0.1 mm to 0.5 mm in thickness.

9. The method according to one of the preceding claims, wherein the intensity of the embossment in the building panel (1 ) is varied by the deflection of the vertical movement of the rotating roller (3) from 10 % to 80 % of the thickness of the building panel (1 ).

10. An apparatus (10) for producing a building panel (1 ) with tapered edges transverse to the direction of the production line in a continuous production process comprising:- a first conveyor belt (21 ) for transporting a building panel (1 ) and- a rotating roller (3) actively rotatable and vertically movable to emboss the building panel (1 ) as to provide a building panel (1 ) with tapered edges transverse to the direction of a production line.1 1 . Apparatus (10) according to claim 10, further comprising:- a second conveyor belt (22), wherein the building panel (1 ) is transported between the first and the second conveyor belt (21 ,22),- a first belt supporting plate (41 ), wherein the building panel (1 ) is pressed against upon being embossed anda second belt supporting plate (42), wherein the first belt supporting plate (41 ) and the second belt supporting plate (42) are angled and positioned in such a way so that they act as an extruder.

12. Apparatus (10) according to claim 10 and 11 , wherein the rotating roller (3) is shaped convex along its length.

13. Apparatus (10) according to any one of the claims 10 to 12, wherein the rotating roller (3) and the first belt supporting plate (41 ) are positioned beneath the first conveyor belt (21 ) and the second belt supporting plate (42) above the second conveyor belt (22), respectively.

14. Apparatus (10) according to any one of the claims 10 to 13, wherein the second belt supporting plate (42) and the first conveyor belt (21 ) are mounted on a frame (6), wherein the frame (6) is vertically movable.

15. The method according to any one of claims 1 to 9 or the apparatus according to any of claim 10 to 14, wherein the building panel (1 ) is a cementitious building panel, especially a gypsum plasterboard or a gypsum fiberboard.

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